1. Field of the Invention
The present invention generally relates to systems and methods for controlling room lighting where an occupancy sensor controls room lighting using standard infrared and/or motion sensor techniques. More particularly, the present invention relates to lighting systems and methods for controlling lighting in an area based on occupancy detection, and dimming features associated with reducing and/or increasing the level of lighting in the area such that a warning can be provided to room occupants when the level of lighting in the room is about to change based on occupancy detection.
2. Discussion of the Background
Conventional light management system for controlling a load circuit where a motion sensor is configured to automatically control the load circuit and/or the night light based on detected motion is disclosed in, for example, U.S. Pat. No. 6,888,323 to Null et al., the entire disclosure of which is hereby incorporated by reference. As described in U.S. Pat. No. 6,888,323 to Null et al., a light management system includes a manual wall switch for manually operating a room light. As shown in FIGS. 2-4 thereof, night light unit provides reduced or low level room lighting when the room light is off. A motion sensor adjusts room light and/or the night light unit based on a detected occupancy of the room. A light sensor unit detects a level of room lighting and adjusting the room light and/or night light unit based on a level of detected room lighting. The manual switch, the night light unit, the motion sensor unit and the light sensor unit 205 are integrated to operate collectively. As shown in a flow chart of FIG. 5, motion in a room is monitored to determine if a room is occupied, and if the room is not occupied and the light is not on then the system continues to monitor for motion in the room. On the other hand, if the room is not occupied and the room light is on, then the room lighting is lowered or reduced by turning off the room light, dimming the room light, turning the night light off, dimming the night light or a combination thereof. Alternatively, or in addition to reducing the level of light emitted from the room light, the level of light emitted from the night light is also increased. If the room is occupied, room lighting conditions are assessed by the light sensor, and if the system determines that there is an insufficient level of room lighting, then the level of room lighting is increased by increasing the amount of light that is emitted by the room light and/or the night light. Alternatively, or in addition to increasing the level of light emitted from the room light, the level of light emitted from the night light is also decreased. The level of light emitted by the night light is integrally associated with the level of light emitted by the room light such that the night light and the room light work together to ensure adequate lighting in the room.
Another conventional device for controlling the level of light in a room as a function of sensed occupancy and ambient light is disclosed in U.S. Pat. No. 5,406,173 to Mix et al., the entire disclosure of which is hereby incorporated by reference. The device described in U.S. Pat. No. 5,406,173 to Mix et al., as shown in FIG. 1 thereof, includes a sensor that detects whether the room is occupied, a timing circuit that detects the duration of time that the room is occupied and unoccupied, a light meter that detects the level of ambient light entering the room, and control circuitry that controls the lights in the room in response to the sensor and light meter. As shown in FIG. 4, this device has three modes of operation: (1) when the room is occupied, it is determined whether the brightness output by lighting unit should be increase or decreased based on increases or decreases of ambient light detected by light meter; (2) when the room is unoccupied for a brief period of time, light control circuit 120 freely adjusts the brightness created by lighting unit 150 up and down to compensate for increases or decreases in the measured ambient light level; and (3) when the room has been unoccupied for a substantial time period, light control unit turns the lighting unit off to remain off until occupancy detector detects the presence of a person in the room again sending a signal to the light control circuit which switches the lighting unit on at the light level determined by light level adjustor.
U.S. Pat. No. 6, 275,163 to Bogorad et al., the entire disclosure of which is hereby incorporated by reference, discloses a conventional occupancy sensor which is combined with an automatic dimmer to control the on/off state of a lamp and its level of brightness. According to U.S. Pat. No. 6, 275,163 to Bogorad et al., automatic switch/dimmer includes an occupancy sensor which provides line output to a microprocessor logic device, which is connected to a key or a present control. As shown in FIG. 3 of U.S. Pat. No. 6, 275,163 to Bogorad et al., the output of the microprocessor logic device is fed to a dimmer module which turns the lamp on or off or can be stepped down from maximum light output to minimum brightness. According to operation flowchart of FIG. 1 of U.S. Pat. No. 6, 275,163 to Bogorad et al., the operation of its automatic switch/dimmer is described as follows. At the start of operation, automatic switch/dimmer device is in attention state, that is monitoring motion while the lamp is off. If no motion is detected, a signal is generated to command the switch/dimmer to maintain the present condition. If motion is detected, a signal is generated to turn the lamps on and increase the brightness level towards maximum brightness. If a the key is not operated, then the lamp goes to maximum brightness. If a key has been activated, a signal is generated to control the lamp brightening to stop at the key setting, whereby the lamp remains on, and the device returns to the attention state. If motion is detected, a signal is generated to retain the lamp at the level selected. This operation will continue as long as motion is detected. If motion is not detected, a signal is generated to cause the lamp to slowly dim. If no motion is further detected, a signal is generated to place the device in its attention state. If motion is detected, then a signal is generated to cause the lamp to go on to its previously selected brightness, and the sensor returns to its attention state.
U.S. Pat. No. 5,489,827 to Xia, the entire disclosure of which is hereby incorporated by reference, discloses a system for controlling the intensity of a lamp including a remote sensing device, which is separate from the light controller and independent of a utility power line, for detecting the presence of an occupant within an area. This patent discloses the use of a remote dimming controller for remotely adjusting the illumination level of a light fixture, such that in the absence of an occupancy signal received from the transmitter within a “second” predetermined period of time (for example, about 12 minutes), the controller automatically reduces the level of illumination produced by the lamp to the lowest non-zero illumination level. When no occupancy signal is received within a “third” predetermined period of time (for example, about 90 minutes), the light controller controls turning off power to the lamp.
None of the prior art systems provide any warning, for example to persons who may still occupy the room, that the level of lighting in the room is about to change based on, for example, the lack of motion detected by the occupancy sensor.